Group B Streptococcal disease has emerged as the principal cause of morbidity and mortality related to infection in newborns in the United States. A prominent feature of the "early-onset" disease is sudden cardio-pulmonary collapse resembling endotoxin shock. It is proposed to study the response of the pulmonary vascular bed in sheep and in newborn lambs to live and heat-killed organisms and to cell components which can be shown to be pharmacologically active. The changes in light and electron microscopy, lung lymph production, pulmonary permeability-surface area product and lung water distribution will be examined before and after infusion. Attempts at pharmacological blocking of the physiological effects will be made.